All of the pressures cooked up for the U.S. space program by far-flung politicians, generals, scientists and the forces of nature converge here at Kennedy Space Center -- a place described by NASA historians as "The Great Interface," where many parts and plans must be fitted together.

Here, the chunky winged orbiters -- the first reusable spacecraft -- come to rest between missions inside 95-foot "high bays," or hangars, where they are encased in beehives of work platforms, hoses and wiring, to be readied for the next launch.

The shuttle's other components -- the external tank and solid rocket boosters that propel it -- are processed in nearby buildings and mated to the orbiter in the giant Vehicle Assembly Building -- so tall it rains inside on occasion, or so technicians say -- before the whole thing is rolled out to the launch pad.

Processing the shuttle for launch, experts say, is one of the most complex operations in the world.

For each minute of a mission aloft, by one estimate provided to Congress, three man-years of labor are spent on the ground.

Standing on the cement floor in one of the orbiter processing bays, where launch schedule pressures are said to be most intense, is like being in a large basement, with the black tile belly of the orbiter as the ceiling. Elevators and stairs lead up to other levels of the work platforms, but only small patches of the craft are visible through the workers' "hive."

For the protection of the hardware, workers are forbidden to carry anything loose into the work areas. Rings must be removed or taped on. All tools are supposed to be tethered. The cargo bay must be kept so ultraclean that workers wear smocks and booties, with masks to cover facial hair. Those who handle dangerous fuels work in rubber suits.

Like the hardware they tend, the ground crews are exposed to conflicting stresses. They are vulnerable to boredom, carelessness and complacency while at the same time, when the shuttles are flying, some face an unpredictable pattern of 50- to 100-hour work weeks. And, of course, lives are on the line.

"There's more danger from being complacent than from being overworked," said one former National Aeronautics and Space Administration quality-assurance official.

In the world of the Great Interface, it can take 53 people 18 hours to move a 60-ton satellite just six feet, inch by inch, into the shuttle cargo bay.

Each section and system of the craft has a set of complications. There is the tile team, for example. The heat-shield tiles, glued over portions of the orbiters to keep them from being incinerated as they reenter Earth's atmosphere, have caused major delays and are still a problem.

A single orbiter might have up to 34,000 tiles, though only a few usually had to be spot-checked or repaired between missions. But each tile is a different shape and has to fit smoothly with the rest of the tile skin.

Looking like some high-tech Michelangelo, a tile technician sits atop a yellow ladder with his neck and back arched backward under the orbiter's belly, daubing a tiny amount of grayish-black compound onto a gap where a tile is missing. Nearby another tile technician sits reading a manual and occasionally glancing at the temperature on a gauge, which will tell him when his tile has set. "The first cure is 15 minutes, then there's a second that takes 10 minutes," technician Steve Moore explains. Replacing one tile might require over 200 inspection stamps.

For those who run the operation, this is a world of endless meetings and "telecons" with other NASA centers and contractors, and of a perpetual blizzard of paperwork. They speak in a jargon unintelligible to outsiders.

The flow directors who schedule the work must take into account not only the specific characteristics of the next flight's mission and cargo, and differences among the orbiters, but computer tapes showing problems from the last mission, lessons learned, needed repairs, availability of spare parts and skilled manpower, limited facilities at the space center, the logistics of moving hardware around the country and other factors.

The scheduling is plotted in thick "flow books," where each worker's tasks are blocked out minute by minute, hour by hour. At least on critical jobs, almost every bolt a worker tightens is supposed to be rubber-stamped as complete and correct by others.

The process generates mountains of paper work, which becomes part of the pressure as launch day nears. Some say the paper work is so overwhelming it almost forces people to find shortcuts through it.

"The pressure manifests itself in funny ways," former NASA engineer Sam Beddingfield said. "The operations guys have thousands and thousands of pieces of paper to close out," he said. "Before a launch, they're running paper counts like mad. They've got to go to that meeting and say whether they've got any open paper work remaining to be done and certified ."

"We do a hell of a lot of work," flow director Tip Talone said. "The percentages say something's going to jump up and bite you some time."